Refrigerant compressor arrangement

ABSTRACT

The invention concerns a refrigerant compressor arrangement with a compressor unit ( 2 ) supported in a case by means of springs ( 12 ) and comprising at least one bolt ( 26 ) with a bolt head ( 25 ), a holder ( 23 ) being arranged between the compressor unit ( 2 ) and at least one spring ( 12 ), the holder ( 23 ) having in its front a recess, in which the bolt head ( 25 ) engages, and which is connected to the spring ( 12 ). It is endeavoured to reduce the noise generation during operation of the refrigerant compressor arrangement. For this purpose, the bolt head ( 25 ) is arranged in the recess ( 24 ) with lateral clearance ( 34 ).

CROSS REFERENCE TO RELATED APPLICATION

Applicant hereby claims foreign priority benefits under U.S.C. § 119 from German Patent Application No. 10 2007 048 936.8 filed on Oct. 12, 2007, the contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention concerns a refrigerant compressor arrangement with a compressor unit supported in a case by means of springs and comprising at least one bolt with a bolt head, a holder being arranged between the compressor unit and at least one spring, the holder having in its front a recess, in which the bolt head engages, and which is stuck together with the spring.

BACKGROUND OF THE INVENTION

Such a refrigerant compressor arrangement is known from, for example, U.S. Pat. No. 4,106,881. The compressor unit has an electric motor with a vertically extending shaft. Above the motor a compressor is arranged, which comprises a piston reciprocating in a cylinder. The piston is driven by the rotary movement of the rotor of the motor. The stator lamination of the motor is kept together by means of bolts. The head of each bolt is inserted in a holder, which again is inserted in a spring. The spring again is mounted on a holding element, which is fixed at the bottom of the case.

A similar embodiment is known from U.S. Pat. No. 4,406,590.

During operation of the compressor unit, the reciprocating movement of the piston of the compressor generates a vibration of the compressor unit. The springs are provided to ensure that such vibrations are not, or at least only to a limited extent, transferred to the case. Vibrations, which should reach the case, would be passed on to the refrigeration appliance, in which the refrigerant compressor arrangement is mounted. When the refrigeration appliance starts vibrating, a partly substantial noise level is generated.

SUMMARY OF THE INVENTION

The invention is based on the task of preventing a noise generation.

With a refrigerant compressor arrangement as mentioned in the introduction, this task is solved in that the bolt head is arranged in the recess with lateral clearance.

In the gravity direction, the compressor unit is still supported by means of the holder. The holder transfers the weight forces of the compressor unit to the spring or the springs, when more or even all springs are connected to the compressor unit via corresponding holders. The oscillations occurring in the compressor unit are substantially directed perpendicularly to the active direction of the springs. The springs support the compressor unit in the gravity direction. When, now, a small movability of the compressor unit in relation to the holder is permitted, a vibration of the compressor unit can move the compressor unit a bit, before it starts moving the holder. Accordingly, the movement finally performed by the holder is smaller than it would be with a form-fitting connection between bolt head and holder. A movement with smaller amplitude will transfer a correspondingly smaller amount of energy to the case via the spring. Accordingly, a noise generation will be reduced. This is particularly the case for a frequency range around 800 Hz, which is particularly inconvenient for a user. In this frequency range, the amplitudes of the vibrations are relatively small, so that a lateral clearance does not have to be excessively large. This means that the bolt head is still guided to a sufficient degree in the holder.

It is preferred that the size of the lateral clearance is in the range from 0.2 to 0.5 mm. For example, the clearance can have a size of 0.25 to 0.35 mm. If the oscillation amplitudes are smaller than this clearance, a lateral contact between the bolt head and the holder is completely avoided, so that an oscillation transfer from the compressor unit via the holder to the spring and thus to the case is completely avoided. If the vibration amplitude is larger, the vibration of the compressor unit will also move the holder. However, as stated above, this movement has smaller amplitude, so that the transfer of energy is reduced.

Preferably, the compressor unit rests on the front side and the recess has a depth, which is larger than an extension of the bolt head in the depth direction. This results in a clearance also in the axial direction. The “axial direction” is the direction of the bolt axis. The compressor unit will then only be supported on the front side of the holder. The bolt head itself is arranged in the holder with a clearance, both circumferentially and at its front side, so that a friction between the front side of the bolt head and the holder is also avoided.

Preferably, a difference between the depth of the recess and the extension of the bolt head has a size in the range from 0.4 to 1 mm. In particular, this clearance can have a size between 0.5 and 0.7 mm. Also this clearance is not particularly large. However, it is sufficient to achieve a decoupling, at least substantially, with regard to oscillations between the compressor unit and the holder.

Preferably, the holder is made of a plastic material that interacts smoothly with the compressor unit, and the holder and the compressor unit bear on each other with smooth surfaces. Thus, it is possible that a relative movement between the compressor unit and the holder occurs, so that a movement transfer from the compressor unit to the holder does not take place, or at least only to a limited extent. The smaller the movement is, which is eventually performed by the holder, the smaller is the risk that noises are transferred to the environment via the case.

Preferably, the bolt head has an undercut in its circumferential surface, behind which projections directed inwardly in the recess engage the holder. This simplifies the manufacturing of the refrigerant compressor arrangement. If the holder is mounted on the bolt head with a clearance, it would fall off during assembly, if the compressor unit with bottom-mounted holder were moved. If, however, an undercut on the bolt head is used, in which the projections of the holder engage, the clearance between the bolt head and the holder can be maintained and the holder would still be fixedly held at the bolt head. After assembling the holder on the bolt head, the compressor unit with the holders hanging downwards in the gravity direction can still be moved without loosing the holders. The holders can then be connected to the springs in a simple manner.

Preferably, the recess is surrounded by a circumferential wall, in which at least two slits extending from the inside to the outside are arranged. These slits cause that the circumferential wall can more easily be outwardly deformed in an elastic manner. This is advantageous, both during the manufacturing of the holder and during manufacturing of the refrigerant compressor arrangement. During manufacturing of the holder, the holder can more easily be removed from a mould, for example an injection mould. The projections themselves do not have to be deformed; on the contrary, the circumferential wall is deformed. When mounting the holder on the bolt head, the holder is, in a manner of speaking, snapped onto the bolt head. When the circumferential wall has sprung back to its original shape, the projections are held in the recess.

Preferably, in the axial direction the projections have a smaller extension than the undercut. In spite of the projections extending into the undercut, this leaves the clearance between the bolt head and the holder in the axial and in the lateral or radial directions. If the compressor unit bears on the front side of the holder, at least one position of the bolt head exists, in which none of the projections is in touch with the bolt head.

Preferably, the holder is made as a hollow body. This means that the holder surrounds a hollow, which can without problems be downwardly open. This saves weight. The lighter the holder is, the less noise energy it can transfer from the compressor unit to the springs and the less are the noises penetrating to the environment.

Preferably, the front side is formed on a side of a front side wall, which has several recesses on the bottom side opposite to the front side. The recesses also provide a mass reduction. At the same time, the supports remaining between the recesses ensure that the front side wall has a sufficient stability to adopt the weight force of the compressor unit.

Preferably, the recesses are open in the direction of the circumferential wall of the holder. Also this is a further measure for saving weight.

Preferably, the holder is made of an electrically isolating plastic material. Thus, it is avoided that currents from the compressor unit, particularly from the motor of the compressor unit, can reach the case via the holder and the spring. Thus, a danger for third parties is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is explained on the basis of a preferred embodiment in connection with the drawings, showing:

FIG. 1 is a vertical section through a refrigerant compressor arrangement;

FIG. 2 is a schematic top view of the opened refrigerant compressor case;

FIG. 3 is a perspective view of a holder with bolts;

FIG. 4 is a perspective bottom view of the holder;

FIG. 5 is a section through a holder; and

FIG. 6 is a section through a holder with bolts and spring.

DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

A compressor unit 2 is arranged in a case 1. A compressor housing 4 is connected to a stator 3 of an electric motor, the compressor housing 4 comprising a cylinder 5 and a bearing 6. In the bearing 6 a motor shaft 7 is supported, which carries a rotor 8 and drives a piston 11 via a crank pin 9 and a connecting rod 10, the piston 11 reciprocating in the cylinder 5. Helical compression springs 12 provide an elastic support for the compressor unit 2 in the case 1. Also a pressure pipe 13 is made to be elastic.

For adopting a cylinder head 14 projecting radially over the stator 3, an enlargement 15 is provided in the case 1. This enlargement also comprises an electric bushing 16 with bushing pins 17, whose inner ends carry a plug 18. In the bottom part of the case 1, both sides of the bushing 16 are provided with concavities 19 and 20. In this way, the wall of the case 1 forms four abutments W1-W4, which can interact with four stops A1-A4, which are arranged on the compressor unit 2. These stops are located at the bottom side of the, in the present case, square stator 3. The edges 21 of the stator 3 are bevelled in such a manner that in all positions they have approximately the same distance to the corresponding abutments W1-W4. The stops A1-A4 project over these bevelled edges in such a manner that they limit a displacement of the compressor unit 2 in any movement direction in the drawing level of FIG. 2 by coming to rest on the abutments. In this connection, the bushing 16 and the plug 18 are safely protected between the concavities 19, 20.

The stops A1-A4 are formed by a collar of a holder 23 for the helical compression springs 12. This holder 23 has a recess 24, into which a bolt head 25 of a bolt 26 is inserted. A holder of metal is welded onto the bottom of the case 1. The holder 23 consists of a refrigerant resistant and electrically isolating plastic material.

In order to prevent an impermissibly large upward displacement of the compressor unit 2, a bracket 29 is fixed by means of bolts on the upper side of the stator on the side opposite the cylinder 5. Further, an angularly shaped projection 30 is fixed at the case 1 with a small distance above the bracket 29. The upper side 31 of the cylinder head 14 has approximately the same distance from the covering wall 32 of the case 1.

During operation of the compressor unit 2, vibrations occur, mainly transversally to the rotation axis of the vertically arranged motor shaft 7. If these vibrations are transferred to the case 1 and from there to elements, in which the case is mounted, for example refrigeration appliances, a relatively high noise load will occur in the environment of the case 1. A part of the oscillations will be suppressed by the helical compression springs 12 and thus only be transferred to the case 1 with a small intensity. None the less, interfering noises will remain, which can penetrate to the environment.

A special embodiment of the holders 23, as shown in the FIGS. 3 to 6, will further reduce the noise generation.

The holder 23 is made of a plastic material, which interacts with the metal of the stator 3 in a low-friction manner. Such a plastic material is known by its commercial name “HALAR”. The material is a fluor polymer, which combines the chemical resistibility to aggressive refrigerants and the lubricating oil with a dimension stability, and which further has a smooth surface. Finally, this plastic material is electrically isolating, so that it prevents the transfer of leakage currents or other currents from the motor to the case 1.

The holder 23 has a front side 31, which is made to be smooth and which interacts with a smooth bearing surface 32 of the stator 3. This means that the stator 3 can slide on the holder 23.

In order to permit this sliding, the bolt head 25 is supported in the recess 23 with a radial and an axial clearance. In this connection, the directions “radial” and “axial” refer to an axis 33 of the bolt 26.

The clearance 34 in the radial direction has a size of 0.1 to 0.5 mm, for example 3 mm. The clearance 35 in the axial direction has a size in the range from 0.4 to 1 mm, for example 0.6 mm. Such a clearance is not large. However, it is sufficient to reduce a corresponding oscillation transfer from the stator 3 to the helical compression spring 12.

The holder has several projections 36, which extend radially into the recess 26. The bolt head 25 has an undercut 37, behind which the projections 36 engage, when the bolt head 25 is inserted in the recess 24.

In this connection, the undercut 37 is dimensioned in relation to the projections 36 in such a manner that, also when the bolt head 25 is inserted in the recess 24, an axial and radial clearance between the holder 23 and the bolt head 25 remains. In other words, the projections 36 have a smaller axial extension than the undercut 37. Thus, when assembling the refrigerant compressor arrangement, the holder 23 can also be mounted on the bolt head 25 from below, when the compressor unit is transported with downwardly hanging holders 23. Together with the undercut 37, the projections 36 retain the holders 23 reliably at the stator. Then, the holders 23 can simply be inserted in the helical compression springs 12 to form a plug connection.

The front side 31 is formed on a front side wall 38. In the circumferential direction, several slits 39 are distributed on this front side wall 38, so that the front side wall 38 can be somewhat outwardly deformed, if this is required. This requirement, for example, occurs, if the holder 23 is injection moulded of a plastic material and has to be removed from a mould after the injection process. In this case, a corresponding core can simply be pulled out from the holder 23, which causes that the projections 36 together with the front side wall 38 can yield radially outwards. A yielding is also appropriate, when the bolt head 25 is inserted in the recess 24.

Otherwise, the holder 23 is made as a hollow body, that is, it surrounds a hollow 40, which extends into an opening 40 in the bottom wall 41 of the holder 23. The lighter the holder 23 is, the smaller is the risk that oscillations will be transferred to the helical compression springs 12 via the holder 23. On the side opposite the front side 31, the front side wall 38 has several recesses 43, which open downwardly and in the direction of the circumferential wall. Also with such an embodiment, mass is saved. Abutments 44 will remain between the recesses 43, by means of which the holders 23 rest on their helical compression springs 12.

While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention. 

1. A refrigerant compressor arrangement with a compressor unit supported in a case by means of springs and comprising at least one bolt with a bolt head, a holder being arranged between the compressor unit and at least one spring, the holder having in its front a recess, in which the bolt head engages, and which is stuck together with the spring, wherein the bolt head is arranged in the recess with lateral clearance.
 2. The refrigerant compressor arrangement in accordance with claim 1, wherein the size of the lateral clearance is in the range from 0.2 to 0.5 mm.
 3. The refrigerant compressor arrangement in accordance with claim 1, wherein the compressor unit rests on the front side and the recess has a depth, which is larger than an extension of the bolt head in the depth direction.
 4. The refrigerant compressor arrangement in accordance with claim 3, wherein a difference between the depth of the recess and the extension of the bolt head has a size in the range from 0.4 to 1 mm.
 5. The refrigerant compressor arrangement in accordance with claim 1, wherein the holder is made of a plastic material that interacts smoothly with the compressor unit, and the holder and the compressor unit bear on each other with smooth surfaces.
 6. The refrigerant compressor arrangement in accordance with claim 1, wherein the bolt head has an undercut in its circumferential surface, behind which projections directed inwardly in the recess engage the holder.
 7. The refrigerant compressor arrangement in accordance with claim 6, wherein the recess is surrounded by a circumferential wall, in which at least two slits extending from the inside to the outside are arranged.
 8. The refrigerant compressor arrangement in accordance with claim 6, wherein in the axial direction the projections have a smaller extension than the undercut.
 9. The refrigerant compressor arrangement in accordance with claim 1, wherein the holder is made as a hollow body.
 10. The refrigerant compressor arrangement in accordance with claim 1, wherein the front side is formed on a side of a front side wall, which has several recesses on the bottom side opposite to the front side.
 11. The refrigerant compressor arrangement in accordance with claim 10, wherein the recesses are open in the direction of the circumferential wall of the holder.
 12. The refrigerant compressor arrangement in accordance with claim 1, wherein the holder is made of an electrically isolating plastic material. 